Methods and systems for generating 3D images are disclosed e.g. in WO 01/88598 A2, WO 2005/117458 A2, the teachings of which are incorporated by reference. The known apparatuses comprise multiple optical modules projecting light beams onto a diffuser screen, thus with proper control, light beams of different color and intensity are propagating from each point of the screen, reconstructing a 3D light field. As a viewer is changing her/his position in the 3D light-field, the perceived 3D image changes accordingly, thereby a true 3D, real life effect is provided.
However, it is a general problem in the prior art solutions that in the process of changing a viewer's position in the 3D light-field, depending on the physical adjustments of the projectors, the diffusion angle of the screen, the optical imperfections, distortions, geometrical or color misalignments, and/or brightness/contrast differences between the projectors, the viewer (observer) will perceive a fluctuation of the intensity, i.e. inhomogeneities will appear at the transitions between two 3D images. In case if the misalignments and/or differences reach a certain value, the angle of divergence (diffusion angle) of the screen is to be set too high to compensate intensity inhomogeneities and display errors, whereby the observer will perceive visual noise caused by the crosstalk between the neighboring 3D images, i.e. where the light beams of neighboring 3D images overlap. For the observer the perceived image will then be blurred, the neighboring views will be simultaneously present in the 3D image and the apparatus will not be capable of displaying images with sharp contours.
Furthermore, the screen diffusion characteristic is a critical factor in such systems, and unfortunately, this Gaussian intensity distribution is inherent in all practical diffusers even in holographic diffusion screens. The uneven total intensity or the undesirable crosstalk is practically unavoidable since these are conflicting requirements; this fact strongly limits the performance of such systems. If the systems are not finely calibrated, serious alignment, color dispersion problems can arise, which again cause a deterioration of the perceived image.